The invention relates to a system having a battery charging device and an onboard electrical power supply stage, said system having a step-up/step-down converter which is jointly used, in particular for the voltage supply of the onboard electrical power supply of an electrically operated vehicle.
A DC voltage converter for an onboard electrical power supply of an electrically operated vehicle often consists of an electrically isolating DC voltage converter and an adjustment stage connected upstream thereof, so that the DC voltage converter can be used in an optimum manner. In particular, in the case of galvanically decoupled DC voltage converters, it is advantageous for an optimum function of the DC voltage converter to work at a constant voltage ratio between input and output voltage, with the result that the circuit must only be designed for a relatively small operating voltage range which makes it possible to design the components for galvanic decoupling, for example a transformer, in a cost-effective manner.
A battery charging device, for example for an energy store of electrically operated vehicles, often consists of a rectifier and a power factor correction stage and an electrically isolated DC voltage converter. The DC voltage converter of a battery charging device often cannot be designed for the entire voltage adjustment range, in particular in the event of a large input and/or output voltage range, with the result that DC voltage converters of this type are either expensive in terms of design or may not work effectively.
The document US 2006/0103359 A1 discloses, for example, a DC voltage converter with improved design for charging a low-voltage battery using a charging device which is designed for charging a high-voltage battery.